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Old 26th January 2007, 13:52   #1
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Default Engine Idling Issue

My car is a 1992 Nissan Altima INLINE 6 Cylinder Manual Transmission "Carb" engine. The car was perfect since purchased.

I am at the moment facing a very peculiar problem since 23rd January related to engine idling.
The car starts with the first twitch of key cold or hot start not an issue. But in the morning first start the engine will turn over with hesitation and ONLY if given MILD throttle will it fire and then within 5 seconds of letting OFF the throttle it will idle well nothing erratic.

after its warmup i drive about 1 km to the first signal and as i approach the lights to stop the engine will idle for say 20 to 30 seconds and then go so low so low so low as if it is going to stall and the engine will shudder the entire car and be that way unless I step on throttle and maintain it to give it that idle feel.
Slot it in 1st 2nd 3rd 4th 5th and there is no finding of anything going wrong even engine is smooth. Do 100/120 and then come to next Stop and the engine will idle for say 20 to 30 seconds and then again start to run so low as if its gonna stall............. as above.

I have checked
Sparkplugs - OK
2 Coils - OK
all hoses - OK
Air Filter - OK clean no hose leaks

Things I plan to do
1) Fuel Filter - replace
2) Carburettor - service (very worried on this as there are no good mechanics who can do a good job if the carb is removed cleaned and installed only 2 mechs who really know to do a skilled job - need Team BHP advice on this)

Any of your comments advice will be much appreciated and I am more of the DIY type so let me have your suggesttions.
thanks
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Old 26th January 2007, 14:07   #2
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2 possible reasons.:

Your engine seems to be running rich. Get the carb cleaned and the float checked.

Also in carb engines there's a tiny valvepin thru which petrol is passed thru on the way to the carb. If this nozzle is clogged even with a tiny dust particle the petrol flow is obstructed and the engine starves - which if corrected by throttling will keep the engine running but flood the carb making it rich. Get this nozzle cleaned.
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Old 27th January 2007, 19:32   #3
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Quote:
Originally Posted by theMAG View Post
2 possible reasons.:

Your engine seems to be running rich. Get the carb cleaned and the float checked.

Also in carb engines there's a tiny valvepin thru which petrol is passed thru on the way to the carb. If this nozzle is clogged even with a tiny dust particle the petrol flow is obstructed and the engine starves - which if corrected by throttling will keep the engine running but flood the carb making it rich. Get this nozzle cleaned.
After a days search I finally found 1 mech who is only into carb tuning. call him a specialist.
Hi got the carb cleaned today. The carb was opened and it just seemed so complicated (TO ME) for a 14 yr machine. The carb has an auto choke, auto timing setup, and the factory pin screw was still intact which was hacksawed and a new springload screw was put in place by the mechanic / tuner. The carb only has one spring load screw to advance the idle speed (if needed).
The setting for RICH LEAN is connected to the carb on the exterior face i.e. facing firewall fastened by 3 screws. On opening by just turning the small knob in it could be set to its very lean or very rich mix at present its set in between. amazing to me to find such tuning adjustment.

The carb was never opened in 5 yrs since my purchase so i got the Fuel Filter changed too the old one was heavy and air was not blowing thru easily.

Also installed a new PCV.

The baby now is really hot with the gas pedal and I am really thrilled with the new feel not that it was bad but now i can see it happy at 50kmph in top with a light foot on gas earlier it had to be above 70kmph to be in 5th.

At the moment the hesitation, stall feeling has gone off but will get to know a correct picture tomorrow morning on cold start (its 8C in bahrain - morning) and later in the day on a warm engine.

thanks buddy.
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Old 27th January 2007, 23:00   #4
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hey do let me know also whats the result / finding would like to learn some more on this and if u have some pictures on the work done do post it to have better idea, btw which mech did u go to??
cheers
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Old 28th January 2007, 11:35   #5
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all was fine until yesterday evening today morning it failed to hold the idle speed without the throttle.
the babe runs fine otherwise.
Points noted:
1) at 80kmph in top if the throttle is pressed right down the acceleration is not smooth like it will buck a couple of times before actually delivering the power. Accelerator pump on carb was tested OK. any comments

2) the above happens in other gears too if the throttle is pressed full, gentle throttle response is perfect.

3) There is some kind of engine raise with each gearshift. The engine feels kind of raised as though throttle pedal is slightly depressed which last for about 2 to 3 seconds - Throttle cable is fine and loose not sticky at all confirmed.

ur coments tbhp tech heads.

Things done
1) accelerator pump checked
2) Vaccum leaks checked / all intake hoses
3) PCV changed
4) Fuel filter changed - fuel hoses all ok

Things planning to do now
FIRST - Timing set up
1) Anti dieseling solenoid on carb test
2) Auto choke if sticky test
3) EGR valve diaphgram test
4) Distributor area rotor etc

let me know which to proceed on first or your comments as at the moment its quite hard to identify the culprit.1

Last edited by 2fast4u : 28th January 2007 at 11:36.
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Old 2nd February 2007, 19:36   #6
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hi tech guys help needed for carb based engine.

After 3 visits to the mech the idle issue issue has been rectified and now the new problem which started today morning is car not starting on cranking up.

Every time i turn the ign key it will crank the engine will kind of stumble shake violently and die. This has happened the first time today morning and theres no history of this happening before. It finally did start after 14 attempts and LIGHT throttle pedal was used as assistance in the last attempt to keep it running.

After the 2 minute warm up the engine is absolutely fine and theres no sign of any problem it idles perfect and alls fine.

Right now am at work so after a gap of approx 6 hrs i tried starting and it did crank but stalled, after 4 attempts similarly with Light throttle pedal as assistance it was fine took it for a spin 12 kms, turned off the engine restarted after 15 seconds started with ˝key turn, waited 10 minutes restarted ˝key turn all OK.

The problem now seems to be cold starting, with engine warm its absolutely fine.

I am looking at a choke open problem, sticky choke or a big vaccum leak (the last problem can be ruled out as all hoses checked, intake manifold secure, carb tightly secured, filter is new, distributor checked.

your inputs please.
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Old 2nd February 2007, 22:26   #7
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I'm no expert (guess that goes w/o saying for most posts on internet forums), but many times the root cause is always something very trivial and easy to fix. It's just hard to find.

I think, you should check 2 things first.
1. Is your battery/alternator ok? If the battery is down, or there's a fault with elec. system, not only will the car give starting trouble, at idling, the battery will act as a heavy load on the engine, causing the rpm drop and engine stalling.

2. There's a cable wire that gets pulled when you press the gas pedal. The cable then pulls smthing else (not your leg :-) ) which pumps more gas into the engine. Since, your engine isn't powering ahead on full throttle, my guess is, there's smthing wrong with the cable, and that's why your engine is acting funny on NO throttle and FULL throttle.

Lemme know, if this helped.
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Old 3rd February 2007, 13:22   #8
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same problem today morning but attempts 5 and engine fired up with LIGHT foot on the throttle for about 20 seconds then its idling fine.

amu@:the problem is not with battery and neither the cable. The throttle pump on the carb is also doing its squirting and release properly - checked, cable also is soft not sticky. The power delivery is fine otherwise there seems to be no issue when the engine is warm or even cold

BUT right now it seems to be the DURATION between engine off to next start and I am zeroing on a carb flooding situation as when it starts there is quite some odour of fuel and some black smoke ONLY AT START.

lets see what the mech can do based on the above info.

I never have dreams but since my "stallion" is suffering i have started seeing the carb in my dream and what next i should check to get this leech cleared.
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Old 5th February 2007, 10:20   #9
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Check for a clogged air jet
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Old 5th February 2007, 11:43   #10
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The mech checked yesterday and found the choke was not functioning properly, waited for engine to cool down and then he set the choke.

Bingo today morning half key start , idling fine, acceleration good - same as it was before the problem started. I'm happy this thing has finally settled.

Only will check to see if its FE is fine 9not a concern in this part of world but still) and also if its not running rich.

the plugs are tan so all seems well.

BTW this is a Hitachi down draft carb. Googling for a weber carb down draft 2 barrel.
Psycho@ if u have some info or guidance much appreciated. thanks

Will still change ALL the vaccum hoses that go to carb.

Last edited by 2fast4u : 5th February 2007 at 11:50.
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Old 5th February 2007, 12:55   #11
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sorry side draft carb
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